Joint prosthesis



Sept- 1962 M. BLACK ETAL 3,053,251

JOINT PROSTHESIS Filed March so, 1959 IN V EN TORS. Maurice 6 lack By Rober/Jaen/b/oen HTTORNEYS Jaenichen, 419 S. Weadock, both of Saginaw, Mich. Filed Mar. 30, 1959, Ser. No. 802,815 6 Claims. (Cl. 128-92) This invention relates to prostheses for introduction to the hip joints of human beings or animals in cases where the neck of the femur or the femoral head has been badly fractured or partially crushed, as well as in cases where it is desired to relieve deterioration of the hip joint caused by diseases such as rheumatoid or hypertrophic arthritis and ankylosing or partially ankylosed conditions or deformities. Operations of the type which are performed to insert the prosthesis of the present invention are known as mould or cup arthroplasties and the present invention relates particularly to improvements in mould or cup prostheses of the type which mount over the head or neck of the femur or a stump thereof.

Prostheses of several designs are known and have been used with varying success in hip surgery. In one design the head of the femur is completely out off and a ball joint having an extending stem is driven into a bore drilled longitudinally down the neck and shaft of the femur. When a prosthesis of this type is used a great part of the femoral head including most of the neck of the femur is, of course, destroyed and if the operation is unsuccessful or only partly successful there is no recourse. Further, such an operation is considerably more difficult to perform than the operation which will be later described, is more hazardous for the patient, and the joint may be less stable since it depends entirely on a solid or rigid load bearing anchorage of the stem in the shaft or neck portion of the femur.

The Smith-Petersen vitallium mould arthroplasty has been employed with some success; however, the Smith- Petersen cup has several disadvantages. The post-operative range of movement depends both on the movement of the cup in the acetabulum and on the movement of the head of the femur in the cup. Partial re-ankylosis due to the growth of fibrous or bony tissue between the flared terminal edge of the cup and the bone is a definite possibility when such a cup is employed. Further, since the Smith-Petersen motion restoration method depends on rotation of the head of the femur in the cup to some degree, the reshaping of the femoral head to conform to the interior of the cup must be precise and the method, which is more difficult to use in cases where a material portion of the femoral head is broken up or crushed, is limited principally to the relieving of disease caused, fixed flexion-adduction deformities of the hip.

One of the prime objects of the instant invention is to provide an improved cup prosthesis which can be used to rebuild the head of the femur when it has been broken up or crushed, without materially reducing the length of the leg and with a minimum sacrifice of bone. Briefly, the invention in one aspect thereof is concerned with a cup for fitting over the femoral head, or portion thereof, which is fixed to the femoral neck or stump thereof if the femoral head has been destroyed so that all of the movement must occur between the cup and the acetabulum.

A further object of the invent-ion is to perfect a cup providing a greater stability which is immediate and having a greater degree of sphericity than known cups so that it can restore normal hip motion without the possibility of the re-ankylosis to which reference was made.

Still another object of the invention is to provide a cup prosthesis as described which simplifies the arthroplasty ansazsi Patented Sept. 11, 1962 with the result that the hospitalization time and recovery period are reduced.

A still further object of the invention is to provide a cup prosthesis designed so that a meticulous fit of the cup on the femoral head and in the acetabulum can be achieved relatively simply to provide a patient with a prosthetized hip joint having excellent, pain-free motion.

With the above and other objects in view, the present invention consists in the combination and arrangement of parts hereinafter more fully described, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims, it being understood that equivalent changes may be made in the various elements which comprise the invention without departing from the spirit thereof or the scope of the appended claims.

In the drawings:

FIGURE 1 is a sectional side elevational view of the cup only, taken on the line 1-1 of FIGURE 2;

FIGURE 2 is a bottom View of the cup or mould;

FIGURE 3 is a side elevational view on a reduced scale showing the cup fixed in position on the head or neck of the femur and pivotal in the acetabulum;

FIGURE 4 is an enlarged, transverse sectional view taken on the line 44 of FIGURE 3;

FIGURE 5 is a side elevational view illustrating a modified embodiment of the invention fixed in place on the femoral head or neck of the femur, and

FIGURE 6 is an enlarged, fragmentary, side elevational view showing the keyway in the cylindrical portion of the prosthesis of FIGURE 5.

Referring now more particularly to the accompanying drawings, wherein in FIGURES 3 and 4 we have shown our improved cup or mould prosthesis C received in the acetabulum or socket 1.0 of the hip bone 11 and clamped in position on the femoral neck 12 of the femur or thigh bone 13, it will be seen that the cup C is generally spherical in shape. The outer surface or wall 14- is semispherical in the sense that it has a spherical portion 14a constituting approximately three quarters of a sphere generated about a central point a, and a cylindrical portion 14b is integral therewith and extends therefrom. As will be seen, the interior wall 15 of the cup C has a hemispherical surface 15a and a portion 15b extending cylindrically and tangentially with respect to the terminal portion of the surface 15a. The wall portion 16 formed between the surfaces 14a and 15a may be about /8 of an inch in thickness and accordingly the wall portion 17 formed between the surfaces 14b and 1511 will be, because of the difference in sphericity of the surfaces 14a and 15a, of reduced thickness and may be on the order of of an inch in thickness. At the inner portion of the wall 17 circumferentially spaced slots 18 extend through to the outer edge of the annular wall 17 and define prongs 19 as shown. The prongs 19 may be formed by drilling a series of circumferentially spaced holes through the wall 17 at the inner edge thereof and thence cutting from the outer edge of the wall 17 through to the holes thus formed tangentially but at an angle so that the prongs 19 taper. Alternatively the material between the prongs I? could be punched out by a suitably constructed triangularly shaped punch and die mechanism. Provided integrally on the prongs 19 at the terminal edges thereof are beads 20 for a purpose which will later be described. The diameter of the surface 1411 will, of course, be in accordance with the size of the person requiring the prosthesis. It is expected that prostheses having an outer circle diameter of 1% inches, 1% inches, 2 inches, 2% inches, and 2% inches, will be satisfactory for most human beings. The corresponding diameters of the inner surfaces 15a will be 1 /2 inches,

1% inches, 1% inches, 1% inches, and 2 inches. Cups will be manufactured in these sizes and will be available so that the surgeon may choose the appropriate size with facility.

It is believed that a description of the operation will aid the readers understanding of the invention and accordingly such a description follows.

Firstly, an anterior ilio-femoral incision is made in the thigh and the muscles are separated according to the Smith-Petersen technique, which is well known in the art, to expose the hip joint. The hip is dislocated by fiexion, adduction, and external rotation in a proper manner to render both the femoral head and neck, and the acetabulum, accessible. Assuming that the arthroplasty is one to relieve an arthritic disease wherein there has been roughening and degeneration of the surfaces of the femoral head and acetabulum, these members will be considered as having remained intact during the disjointing operation.

The diameter of the acetabulum is next accurately measured and a cup C is selected having an outside surface diameter corresponding most closely thereto. Thereafter, the acetabulum is reamed accurately to the spherical shape of the surface 14a, allowing, however, for A of an inch clearance for relative movement of the cup C in the acetabulum. Then the femoral head is reamed accurately to the point where it fits snugly the inside surface 15a of the cup selected. The cup C is to have a tight fit on the femoral head and is placed over the femoral head and tamped gently into place when a near perfect fit is achieved.

The amount of material removed in reaming the acetabulum and the femoral head will correspond to the thickness of the cup introduced so that the length of the patients leg will be the same after the surgery as prior thereto. With the cup in position on the femoral head and neck, the prongs 19 are usually, except for possibly a few prongs, initially out of engagement with the inner portion of the femoral neck. Because of the irregularity of this neck portion of the femur (see FIGURE 4), the prongs 19 are important to providing a stable joint in which the femoral head does not move within the cup C. As has been noted, the prongs 19 are of reduced thickness and can be bent in to firmly clamp the neck portion of the femur.

The beads 20 provide purchase for the tool which squeezes each lug independently in to the neck of the head of the femur and the tips of the pliers which are used fit into the radius b formed between the bead 20 and wall 14b and do not tend to slip off. While one 5 prong or two prongs would, for prongs of of an inch in thickness, provide relatively little clamping stability, when all of the prongs are clamped into the bone, the cup is rigidly fixed or supported in position and the joint has more than adequate stability. This construction eliminates the possibility of the femoral head moving within the cup, because the prongs 19 follow the contour of the neck portion of the femur. When the femur or thigh and hip are then rejointed with the cup received in the acetabulum, immediate stability is achieved and the prosthesis cannot work loose.

In the embodiment of the invention shown in FIG- URES 5 and 6, a modified cup is shown utilized in a situation in which a material portion of the femoral neck has broken off. While the embodiment of the invention already described could be used in this situation in much the same way, some loss of length in the leg would occur. In the case of the cup prosthesis shown in FIG- URE 5, the cup C is formed with a semi-spherical surface 14a corresponding to the surface 14a and an inner semi-spherical surface 15a corresponding to the surface 15a. The surface 15a is, however, of less sphericity than surface 15a and the surface 15b is of correspondingly greater length and is finely threaded as shown. The cylindrical portion 17' is of such outer diameter as 4 to fit within the annular surface 15b and its surface 141: is correspondingly threaded as shown. Slots 18' are provided; however, the marginal walls are more acutely angled than the marginal walls of the slots 18 previously described so that the prongs 19 terminate in ends which may be termed pointed.

The operation proceeds similarly to the point of reaming the acetabulum, which is done. In this modified operation the femoral head is not reamed as previously although the broken off portion 21 may be roughened. Instead, the interior of the cup C is filled with a mixture of bone chips and bone glue, as indicated at 22, the bone chips being taken from the reaming of the acetabulum or formed by breaking up a split off portion of the femoral head. Prior to filling the cup C with bone chips and inserting it over the stump of the femoral neck, the trochanteric region is slotted as at 23 to receive the pointed ends of the prongs 19 and the wall 17 is axially adjusted relative to the spherical portion of the cup C so that the length of the patients leg will remain the same as prior to the operation. The spherical portion of the cup C is prevented from relative rotation with the cylindrical wall portion 17 by a set screw 24, having a special head shaped exactly to the spherical surface 14a, which is snugly received in an axially extending keyway 25 provided in the wall 17'. The set screw 24 is disposed in the under portion of the wall of the spherical portion of the prosthesis and its head is flush with surface 14a or inset slightly therefrom. It has been found that the bone chips and bone glue mixture will grow to the stump of the femoral neck and, in effect, restore it, and, of course, the stability of the joint is considerably increased for this reason. Further bone will grow in the slot 23 in the trochanteric region and increase the stability of the joint.

With the prosthesis of the instant invention, in which the prongs 19 or 19' lightly clamp the cup in position, any build-up of bone between the end walls of the beads 20 of the prongs and the bone itself can only improve the stability of the joint and restoration of the normal motion between the leg and the hip is not endangered. The femoral head need not be cut off and it is unnecessary to drill into the femur, so that the operation can be performed more rapidly, with a minimum sacrifice of original bone, and with less danger to the patient. If, for some reason, the operation should be only partly successful, a corrective operation can still be performed.

While the cups C and C have been described as hip joint prosthesis, it is believed that they may be quite suitable also for repairing the shoulder joint or possibly the knee joint with a suitable modification of the relatively moving joint surfaces.

The cups C and C are formed of a ductile, stainless steel which is compatible with the human body. The prongs 19 and 19' with the slots between them are of great significance since bone grows in the slots between the prongs to key the cup in position. Further, the prongs 19 and 19', when bent in, provide a clearance permitting a greater range of movement of the cup in the acetabulum.

It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that various changes may be made in the various elements to achieve like results without departing from the spirit of the invention or the scope of the appended cl ims.

We claim:

1. In a joint prosthesis mounted in the joint socket of a human being or animal on a joint or portion functionmg as a joint; a generally spherical member having an outer spherical surface of substantially greater than hemispherical sphericity but terminating short of complete sphericity; a generally cylindrical section for said member extending from the terminus of said member and h0lextending from the terminus of said member and hollowed to accommodate the said joint or portion; means incorporated with said section for fixing said generally cylindrical section fast on said joint or portion; said memher being bored to provide a cylindrical surface of such size as to receive said generally cylindrical section; and means incorporated with one of said member and section for fixing said cylindrical section in various axially extended positions relative to said surface.

2. The combination defined in claim 1 in which said member is provided with a threaded bore and said generally cylindrical section is threaded to be received there- 3. The combination defined in claim 1 in which said generally cylindrical section has a very thin wall of uniform thickness and has axially extending slots of substantial Width at circumferential intervals to form prongs bendable in to clamp on said joint or portion; said prongs having beads on the outer surfaces thereof at their ends.

4. A method of joint prosthesis for living creatures comprising the steps of; adjusting the length of said prosthesis to correspond to the normal length of the femoral head and neck; filling the cup-like prosthesis with bone chops and bone glue in the portion thereof not to be filled with bone; mounting the hollow, cuplike prosthesis over a dislocated joint or portion of bone functioning as a joint; fixing said prosthesis in position on the said joint or portion; and inserting the said prosthesis in the joint socket of the creature.

5. In a rigid joint prosthesis for mounting in the joint socket of a human being or animal on a joint or portion functioning as a joint; a hollowed, rigid metal cup-like member having an outer spherical surface of substantially greater than hemispherical sphericity but terminating short of complete sphericity for reception in a human or animal joint socket; said member having a cylindrical, metal skirt portion of reduced wall thickness relative to said spherical surface having cylindrical exterior and interior wall surfaces and defining a thin, ductile Wall of substantially uniform thickness extending from the terminus of said spherical surface and having cut out portions forming circumferentially spaced apart, axially extending, separated legs spaced by slots through the said Wall and bendable in to the bone and between which bone can grow to key the cylindrical portion in position, said slots leading from the outer end of said cylindrical skirt portion axially but terminating short of said spherical surface.

6. In a joint prosthesis for mounting in the joint socket of a human being or animal on a joint or portion func tioning as a joint; a hollowed, cup-like member having an outer spherical surface for reception in a human or animal joint socket; said member having a cylindrical portion defining a thin and ductile wall extending axially and having cut out portions forming circumferentially spaced apart, axially extending legs receivable in a groove formed in the joint or portion functioning as a joint which can he bent in to the bone and between which bone grows to key the cylindrical portion in position; and peripherally projecting beads on the exterior walls of the ends of said legs receivable within said groove to permit bone to grow between and in behind said beads and axially key said prosthesis in position while at the same time providing purchase for the tool used to deform said legs in to the irregular shape of the bone.

References Cited in the file of this patent UNITED STATES PATENTS 2,537,070 Longfellow Ian. 9, 1951 2,668,531 Haboush Feb. 9, 1954 FOREIGN PATENTS 7203092 Great Britain Dec. 15, 1954 876,739 Germany May 18, 1953 1,017,927 France Oct. 1, 1952 1,122,634 France May 28, 1956 

